This is a note to let you know that I've just added the patch titled
drm/vmwgfx: Add unwind hints around RBP clobber
to the 6.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-vmwgfx-add-unwind-hints-around-rbp-clobber.patch
and it can be found in the queue-6.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit aeb6b7c6b6ef84ab496189cdbc698426092aa46c
Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Date: Mon Jun 5 09:12:22 2023 -0700
drm/vmwgfx: Add unwind hints around RBP clobber
[ Upstream commit a9da8247627eefc73f909bf945031a5431a53993 ]
VMware high-bandwidth hypercalls take the RBP register as input. This
breaks basic frame pointer convention, as RBP should never be clobbered.
So frame pointer unwinding is broken for the instructions surrounding
the hypercalls. Fortunately this doesn't break live patching with
CONFIG_FRAME_POINTER, as it only unwinds from blocking tasks, and stack
traces from preempted tasks are already marked unreliable anyway.
However, for live patching with ORC, this could actually be a
theoretical problem if vmw_port_hb_{in,out}() were still compiled with a
frame pointer due to having an aligned stack. In practice that hasn't
seemed to be an issue since the objtool warnings have only been seen
with CONFIG_FRAME_POINTER.
Add unwind hint annotations to tell the ORC unwinder to mark stack
traces as unreliable.
Fixes the following warnings:
vmlinux.o: warning: objtool: vmw_port_hb_in+0x1df: return with modified stack frame
vmlinux.o: warning: objtool: vmw_port_hb_out+0x1dd: return with modified stack frame
Fixes: 89da76fde68d ("drm/vmwgfx: Add VMWare host messaging capability")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Link: https://lore.kernel.org/oe-kbuild-all/202305160135.97q0Elax-lkp@xxxxxxxxx/
Link: https://lore.kernel.org/r/4c795f2d87bc0391cf6543bcb224fa540b55ce4b.1685981486.git.jpoimboe@xxxxxxxxxx
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/include/asm/unwind_hints.h b/arch/x86/include/asm/unwind_hints.h
index 01cb9692b160a..85cc57cb65392 100644
--- a/arch/x86/include/asm/unwind_hints.h
+++ b/arch/x86/include/asm/unwind_hints.h
@@ -76,9 +76,18 @@
#else
+#define UNWIND_HINT_UNDEFINED \
+ UNWIND_HINT(UNWIND_HINT_TYPE_UNDEFINED, 0, 0, 0)
+
#define UNWIND_HINT_FUNC \
UNWIND_HINT(UNWIND_HINT_TYPE_FUNC, ORC_REG_SP, 8, 0)
+#define UNWIND_HINT_SAVE \
+ UNWIND_HINT(UNWIND_HINT_TYPE_SAVE, 0, 0, 0)
+
+#define UNWIND_HINT_RESTORE \
+ UNWIND_HINT(UNWIND_HINT_TYPE_RESTORE, 0, 0, 0)
+
#endif /* __ASSEMBLY__ */
#endif /* _ASM_X86_UNWIND_HINTS_H */
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h b/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h
index 0b74ca2dfb7bd..23899d743a903 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h
@@ -105,10 +105,14 @@
flags, magic, bp, \
eax, ebx, ecx, edx, si, di) \
({ \
- asm volatile ("push %%rbp;" \
+ asm volatile ( \
+ UNWIND_HINT_SAVE \
+ "push %%rbp;" \
+ UNWIND_HINT_UNDEFINED \
"mov %12, %%rbp;" \
VMWARE_HYPERCALL_HB_OUT \
- "pop %%rbp;" : \
+ "pop %%rbp;" \
+ UNWIND_HINT_RESTORE : \
"=a"(eax), \
"=b"(ebx), \
"=c"(ecx), \
@@ -130,10 +134,14 @@
flags, magic, bp, \
eax, ebx, ecx, edx, si, di) \
({ \
- asm volatile ("push %%rbp;" \
+ asm volatile ( \
+ UNWIND_HINT_SAVE \
+ "push %%rbp;" \
+ UNWIND_HINT_UNDEFINED \
"mov %12, %%rbp;" \
VMWARE_HYPERCALL_HB_IN \
- "pop %%rbp" : \
+ "pop %%rbp;" \
+ UNWIND_HINT_RESTORE : \
"=a"(eax), \
"=b"(ebx), \
"=c"(ecx), \
